1. Field of Art
The present disclosure relates to a method for testing a charge generation layer and to a process for manufacturing electrophotographic photoreceptors on a large scale.
2. Description of the Related Art
An electrophotographic photoreceptor of an electrophotographic apparatus includes a support member, an undercoat layer on the surface of the support member, and a charge generation layer containing an organic charge generation material and a charge transport layer containing a charge transport material, disposed on the undercoat layer.
The electrophotographic photoreceptor is manufactured by applying a charge generation coating liquid in which a charge generation material and a binding resin are dissolved or dispersed in a medium onto the surface of the support member to form a coating film, and drying the coating film.
The coating liquid is evenly applied to a uniform thickness so that the electrophotographic photoreceptor can form images having no unevenness. However, stagnation of and finger touch on the coating liquid during coating operation can cause unevenness in the thickness of the coating film. Also, evaporation of the solvent may adversely affect the evenness in thickness. Since large unevenness in the thickness of the coating film can result in image defects, coating films must be screened for uneven thickness in a testing step in the manufacturing process of electrophotographic photoreceptors. In particular, unevenness of the charge generation layer in thickness (hereinafter may be referred to as the defect of the charge generation layer) considerably affects the sensitivity of the electrophotographic photoreceptor, and accordingly tends to cause image defects.
For testing the charge generation layer for unevenness in thickness, the electrophotographic photoreceptor may be visually observed, or subjected to the test of irradiating the electrophotographic photoreceptor with light and receiving the reflected light with a light-receiving device. Japanese Patent Laid-Open No. 2003-75362 discloses a test method for testing electrophotographic photoreceptors for interference fringes and appearance defects at one time. In this method, electrophotographic photoreceptors are irradiated with light having a single wavelength, and a line sensor camera receives the light regularly reflected from the electrophotographic photoreceptor and detects unevenness in the thickness of the charge generation layer by image processing.
The applicant has found that when an undercoat layer having a transmittance of 1% or more for light having a wavelength in the visible region is formed directly on an aluminum cylindrical support member formed by extrusion and drawing and having a periphery not subjected to cutting work, the undercoat layer may not be able to cover the unevenness of the support member.
The unevenness of the aluminum cylindrical support member formed by extrusion and drawing whose periphery has not be subjected to cutting work is in the form of streaks extending in the generating line direction of the support member. Unlike the unevenness in the thickness of the charge generation layer considerably affecting sensitivity, the unevenness of the support member does not easily result in image defects. Even if some unevenness is detected in the support member in a test, such unevenness should be judged to be not defective as long as unevenness in the thickness of the charge generation layer is not detected.
However, if unevenness is detected in a test of the charge generation layer for unevenness in thickness after the charge generation layer has been formed on the undercoat layer on the support member, it cannot be determined whether the detected unevenness results from an uneven thickness of the charge generation layer, which may cause an image defect, or the uneven support member.